I cut my girls loose with acrylic craft paint, some images cut out from back issues of "O" magazine, some glue, watercolours, and permanent pens. We talked about their choices, what drew them to certain images, and explored how their images looked on different- colored backgrounds. They proudly signed their work, then ran off to play.
Art without attachments to what they're creating. Art with no plan and no pressure to make it look like something. Art for its own sake. Art matters.